An image acquisition system typically includes an array of photosensitive pixels which are successively switched in a circuit to connect to A/D converter cells. The photosensitive pixels receive incoming light, and produce an analog output indicative of the information in each pixel in the array. That analog information is then coupled to an analog to digital converter which converts the analog information into a digital value indicative thereof. Typically the elements of the array are connected to different analog to digital converter elements. The pixels are successively converted into digital values.
One way of carrying out this analog to digital conversion is via successive approximation A/D converter cells. However, the variation between such successive approximation cells causes an inherent variation in the output signals. This can cause fixed pattern noise, that is, a noise pattern which is superimposed over the actual image being obtained.